JP4696249B2 - Shape measuring method and apparatus - Google Patents

Description

  The present invention relates to a shape measuring method and apparatus for measuring the shape of a surface to be measured.

  With the development of precision machining technology in recent years, quality control regarding the surface shape of machined parts has become important. And if in-process holistic surface shape inspection of manufactured parts is possible, it is very effective in suppressing defective products from the factory. At present, stylus-type shape measuring devices and laser interferometers are used for shape inspection, but these devices require a high set position accuracy of the measurement object and are not susceptible to mechanical vibrations. Since a measurement chamber is required, it cannot be applied to an in-process surface shape inspection apparatus.

  A conventional surface shape measuring device that scans and measures the surface of a measurement object point by point has a long measurement time because the scanning speed over several centimeters is as slow as several tens of seconds, and is therefore susceptible to mechanical vibration. was there. Further, the scanning optical system is expensive, and it is insufficient as an in-process total surface shape inspection apparatus. A surface shape measuring apparatus that solves these insufficient points is disclosed in Patent Document 1.

  This surface shape measuring apparatus causes a light beam emitted from a light source to enter a surface to be measured via a scanning optical system, and measures the inclination distribution by recognizing the light beam reflected by the surface to be measured with a position sensor, A shape measuring device that obtains the shape of the surface to be measured by integrating the obtained slope distribution with an arithmetic unit, and changes the luminous flux emitted from the light source in real time by the luminous flux redirecting means. The light beam redirected by the means is reflected by one or a plurality of plane mirrors and is incident on the measured surface via a concave mirror provided in a state of facing the measured surface, and the turning angle by the light beam redirecting means. The scanning optical system is configured so that the surface to be measured can be scanned by changing the light beam, and the light beam redirecting means and the position sensor are conjugates of the concave mirror to each other via the plane mirror or the surface to be measured. Set at the point It is intended.

In the first embodiment of Patent Document 1, the light beam redirecting means and the position sensor are arranged at the conjugate distance of the concave mirror. The meaning of “arranged at the conjugate distance” means the optical path S ₁ -R-M. When L = L1 and the optical path M−Q−S ₂ = L2, (1 / L1) + (1 / L2) = 2 / R is established. With respect to the positions of the plane mirror and the surface to be measured, the distances from the light beam redirecting means are equal, so that L1 = L2 = R, and (1 / L1) + (1 / L2) = 2 / R holds. This state is a special case, and the paragraph “0043” in the specification expresses that the concave mirror has no aberration. When there is no aberration, the direction of the reflected light from the surface to be measured is proportional to the shape of the surface to be measured. Therefore, as described in paragraph “0051” of the specification, from the light spot position displacement Δ, The shape of the surface to be measured is obtained.

On the other hand, also in the second embodiment of Patent Document 1, the light beam turning means and the position sensor are arranged so that (1 / L1) + (1 / L2) = 2 / R is established. However, since L1 is not equal to L2, the light spot position displacement (corresponding to the position of S2) proportional to the shape of the surface to be measured appears on the surface of the beam redirecting means. For this reason, a lens is used to form an image on the surface of the position sensor on the surface of the beam redirecting means. That is, the second embodiment is a configuration when there is no position sensor at the conjugate point of the concave mirror (S2 on the surface of the light beam diverting means) (because there is a light beam diverting means). The position sensor is arranged at one conjugate distance of the lens, and one conjugate distance of the concave mirror is the other conjugate point of the lens (the image is formed by the lens described above).
JP 2004-279132 A

  In this surface shape measuring apparatus, when the surface shape of the measurement target is to be measured with an error of 10 nanometers or less, it is necessary to set the measurement target surface with an error of 1 micron or less with respect to the front-rear direction of the measurement target surface. However, in actual measurement, there is usually a position setting error of about 100 microns, so an error of the order of several microns occurs in the measurement result of the surface shape. The surface shape generated as the measurement error is a quadratic function with respect to the one-dimensional scanning direction of the laser beam. For this reason, when the surface to be measured includes a surface shape component of a quadratic function, there is a big problem that the surface shape cannot be accurately measured with the surface shape measuring apparatus disclosed in Patent Document 1.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention has an object to provide a shape measuring method and apparatus capable of accurately measuring a surface shape including a surface shape component of a quadratic function without strict conditions on the position setting accuracy of a measurement target. To do.

  In the shape measuring method according to claim 1 and the shape measuring apparatus according to claim 4 of the present invention, the light beam emitted from the light source by the scanning optical system is scanned on the surface of the measurement object, and the reflected light beam reflected by the measurement object is measured. By detecting the propagation direction with a light propagation direction detection system and performing a calculation based on the detection result, a shape measuring method for obtaining the surface shape of the measurement object (or by performing a calculation with a calculation device based on the detection result) A shape measuring apparatus for determining a surface shape of the measurement object), wherein the scanning optical system is changed by a light beam diverting unit for diverting a light beam emitted from the light source in a desired direction, and the light beam diverting unit. A plane mirror that reflects the directed light beam, and a concave spherical mirror that is provided opposite to the plane mirror and reflects the light beam reflected by the plane mirror and enters the object to be measured. The planar mirror and the concave spherical mirror are arranged so that the optical path length from the luminous flux changing means through the plane mirror to the concave spherical mirror is equal to the curvature radius of the concave spherical mirror. The light propagation direction detection system includes a lens on which a reflected light beam reflected by the measurement object is incident, and an optical position detector disposed at a position separated from the lens by a focal length of the lens. .

  In this way, since the surface shape can be measured because the propagation direction of the reflected light beam from the measurement target surface varies depending on the inclination of the measurement target surface, the optical system can accurately detect angular shake. Therefore, there are no strict conditions for the position setting accuracy of the measurement object, and the surface shape including the surface shape component of the quadratic function can be measured accurately.

  The shape measuring method according to claim 2 and the shape measuring apparatus according to claim 5 of the present invention are configured such that the reflected light beam reflected by the measurement object is reflected by the light beam diverting means and reflected by the light beam diverting means. A second plane mirror is provided for reflecting the reflected light flux toward the lens.

  In this way, since the light propagation direction detection system can be arranged at a position away from the scanning optical system, it is easy to configure an apparatus (shape measuring apparatus) used for the shape measurement.

  In the shape measuring method according to claim 3 and the shape measuring apparatus according to the present invention, the detection position Δ (Δ = 2θf, θ is the measurement object) of the optical position detector, which is the detection result of the light propagation direction detection system. The position distribution Δ (x) of the detection position Δ with respect to the scanning direction position x is measured by sequentially calculating the inclination angle θ based on the inclination angle of the surface of the lens, and f is the focal length), and the following equation is calculated: By doing

The surface shape r (x) of the measurement object is obtained.

  In this way, the surface shape of the measurement object can be easily calculated from the detection position of the optical position detector.

  According to the first and fourth aspects of the present invention, it is possible to provide a shape measuring method and apparatus capable of accurately measuring a surface shape including a surface shape component of a quadratic function without a strict condition on the position setting accuracy of a measurement target. .

  According to claims 2 and 5 of the present invention, the apparatus configuration is facilitated.

  According to claims 3 and 6 of the present invention, the surface shape of the measurement object can be easily calculated.

  Hereinafter, preferred embodiments of a shape measuring method and apparatus according to the present invention will be described with reference to the accompanying drawings.

  First, the main points of the present invention will be described.

  There is a measurement principle in which a one-dimensional surface shape is measured by detecting an angular fluctuation of a laser beam, which is a light beam proportional to the inclination of the surface to be measured, and integrating the surface inclination. As a one-dimensional surface shape measuring device applying this measurement principle, it is composed of an optical system that scans a laser beam one-dimensionally on the surface to be measured at high speed and simultaneously detects the angular deflection of the laser beam due to the inclination of the surface to be measured. Invented a surface shape measuring device. The scanning optical system of the present invention is configured by using a rotating scanner mirror, a plane mirror, and a concave spherical mirror. Therefore, it is a very inexpensive high-speed scanning optical system.

  A surface shape measuring device using a similar scanning optical system is disclosed in Patent Document 1, but in this measuring device, the amount of the reflected laser beam from the surface to be measured varies depending on the inclination of the surface to be measured. The surface shape is measured. For this reason, as described above, there is a serious problem that the position setting accuracy of the measurement target is strict and the component of the surface shape that is a quadratic function in the one-dimensional scanning direction of the laser beam cannot be measured.

  In the present invention, in order to solve these problems, the positional relationship between the plane mirror and the concave spherical mirror is set, and the reflected laser beam subjected to the angular deflection is guided onto the photodetector by the lens. The surface shape is measured because the propagation direction of the reflected laser beam from the surface to be measured differs depending on the inclination of the surface. For this reason, it is an optical system that can accurately detect angular shake, and there is no strict condition for the position setting accuracy of the measurement object, and the surface shape including the surface shape component of the quadratic function can be measured accurately.

  From the above characteristics, in the surface shape measuring apparatus according to the present invention, high accuracy is not required for setting the position of the measurement object, so that the measurement object can be easily set. In addition, since the measurement time of a one-dimensional surface shape over several centimeters is very short, on the order of milliseconds, and no seismic isolation device is required, in-process total surface shape inspection in a bad environment with many mechanical vibrations. It is an effective measuring device.

  Next, the principle of surface shape measurement used in the present invention will be described with reference to FIG.

  The laser beam emitted from the laser light source 10 is incident on the point P on the surface S of the measurement object 30. The laser beam reflected at the point P passes through the lens 41 and enters the point O on the light beam position detector 42 if the measurement target surface S is flat. However, PO is the optical axis of the lens 41, and the detection surface of the light beam position detector 42 is perpendicular to the optical axis. Further, the distance between the lens 41 and the light beam position detector 42 is equal to the focal length f of the lens 41. If the tilt angle, which is the angle between the tangent line at the point P on the surface S of the measuring object 30 and the x axis, is θ, the reflected laser beam from the point P forms an angle of 2θ with the straight line PO. Therefore, the position Δ of the laser beam spot as the light beam incident point on the surface of the light beam position detector 42 at this time becomes Δ = 2θf by the action of the lens 41 if θ is very small. The output of the light beam position detector 42 is a value proportional to the position Δ of the light beam, and the tilt angle θ can be measured. If the beam spot on the surface of the measuring object 30 is scanned in the x-axis direction and the position distribution Δ (x) of the light beam is measured,

The one-dimensional surface shape r (x) of the measuring object 30 can be measured by Equation 2.

  An embodiment of the present invention based on the above principle will be described with reference to FIGS.

  Reference numeral 10 denotes a laser light source. For example, a gas laser or a semiconductor laser may be used. Reference numeral 11 denotes a lens for adjusting the size of the beam spot diameter on the surface of the measuring object 30. Reference numeral 20 denotes a scanner mirror as a beam turning means for scanning a beam spot on the surface of the measuring object 30 by reflecting (turning) the laser beam emitted from the laser light source 10, for example, rotating a motor A flat mirror, half mirror, polygon mirror, galvano scanner, etc. attached to the shaft are used. The scanner mirror 20 is also used to reflect a reflected laser beam from the surface of the measurement object 30 so as to enter the flat mirror 40. Reference numeral 21 denotes a flat mirror that reflects the laser beam reflected by the scanner mirror 20 and enters the concave spherical mirror 22. Reference numeral 22 denotes a concave spherical mirror that reflects the laser beam reflected by the plane mirror 21 and enters the measurement object 30. Reference numeral 40 denotes a plane mirror that reflects the reflected laser beam reflected by the scanner mirror 20 and makes it incident on the lens 41. Reference numeral 41 denotes a lens for detecting the propagation direction of the reflected laser beam from the measurement object 30. Reference numeral 42 denotes a light beam position detector, which may be a CCD element, PSD, photodiode array, or the like. 51 is a personal computer (hereinafter referred to as an arithmetic unit) that performs an operation for obtaining the one-dimensional surface shape r (x) of the measurement object 30 described above with respect to the position detection signal obtained by the light beam position detector 42. PC).

  First, in FIG. 2, a thin laser beam from the laser light source 10 passes through the lens 11 and is incident on the rotation center A point of the scanner mirror 20. The size of the beam spot diameter on the surface of the measuring object 30 is adjusted according to the position of the lens 11. When the scanner mirror 20 is in the rotational position as shown in the figure, the reflected laser beam from the point A is incident on the point Q of the plane mirror 21 and reaches the point C of the concave spherical mirror 22. The optical axis of the concave spherical mirror 22 is in the z-axis direction, and the center of rotation A of the scanner mirror 20 is on this optical axis. The angle formed by the path AQ and the z axis is φ. In such an arrangement, when the length AQC is equal to the radius of curvature of the concave spherical mirror 22, the reflected laser beam from the point C of the concave spherical mirror 22 returns along the same path CQ and reaches the point P of the measurement target 30. When the tilt angle θ, which is the angle between the measurement target surface and the x-axis at the point P, is θ = 0, the reflected laser beam from the point P travels in parallel with the path AQ, reaches the point R of the scanner mirror 20, and reaches the plane. Reflected at the T point of the mirror 40. The path RT is parallel to the laser beam from the laser light source 10. The laser beam reflected by the plane mirror 40 enters the lens 41. The optical axis of the lens 41 is parallel to the z axis. A light beam position detector 42 is disposed at a position away from the lens 41 by the focal length f of the lens 41, and the laser beam that has passed through the lens 41 intersects with the point O on the light beam position detector 42, that is, the optical axis. O is reached. In this case, the position Δ of the light beam is Δ = 0, and the inclination angle θ of the surface to be measured is detected as θ = 0.

  When the scanner mirror 20 rotates, the angle φ changes, and the beam spot on the surface of the measuring object 30 is scanned in the x-axis direction. When the surface of the measuring object 30 is a flat surface parallel to the x-axis as shown in the figure, the reflected laser beam from the surface of the measuring object 30 always passes through the point X on the optical axis, and the light from the concave spherical mirror The angle formed with the axis is φ. When this reflected laser beam is reflected by the scanner mirror 20, the laser beam becomes parallel to the optical axis of the lens 41 and reaches the point O on the light beam position detector. The distance h between the laser beam and the optical axis is h = 2dφ.

  Next, as shown in FIG. 3, when the tilt angle of the surface of the measuring object 30 is θ, the reflected laser beam from the surface of the measuring object 30 touches the angle by an additional angle 2θ compared to the flat surface. When it is raised and incident on the lens 41, the angle between the laser beam and the optical axis of the lens 41 is 2θ, and the position reaching the point on the light beam position detector 42 is a position away from the point O by Δ = 2θf. .

  The beam spot on the surface of the measuring object 30 is scanned in the x-axis direction by the rotation of the scanner mirror 20, and the output of the light beam position detector 42 by this scanning is taken into the personal computer 51. The position Δ of the light beam and the inclination angle θ of the surface to be measured are obtained from the captured detection data, and the surface shape r (x) is calculated.

  2 and 3 are drawings drawn on the xz plane, and the propagating laser beam is drawn so as to be blocked by the plane mirror 40, the concave spherical mirror 22, or the plane mirror 21. In the apparatus, as shown in FIG. 4, the arrangement is such that these laser beams are not blocked. The concave spherical mirror 22 has a thin rectangular shape in the y-axis direction so that the beam path AQ is not blocked. The plane mirror 21 and the concave spherical mirror 22 are parallel to the x-axis, but are inclined with the x-axis direction as the rotation axis. Therefore, the beam paths QC and CP are not parallel to the xz plane, and the plane mirror 21 is also formed into a thin rectangle in the y-axis direction, so that the beam path CP is not blocked by the plane mirror 21. Yes.

  Here, the difference between the shape measuring apparatus disclosed in Patent Document 1 and the shape measuring apparatus according to the present invention will be described.

  As described in paragraph “0059” in the specification of Patent Document 1, the position of the plane mirror of the first embodiment is impractical and impractical. For this reason, the embodiment of the present invention has the same configuration as that of the second embodiment of Patent Document 1, and the distances from the light beam redirecting means are different with respect to the positions of the plane mirror and the surface to be measured. However, in Patent Document 1, since the optical path S1-R-M is always shorter than the optical path M-Q-S2, the lengths of the optical path S1-R-M and the optical path M-Q-S2 are conjugate distances of the concave mirrors. Thus, the positions of the plane mirror and the surface to be measured are determined. And in order to detect the movement of light on the surface of the beam redirecting means at one conjugate distance of the concave mirror, the position sensor is arranged at one conjugate distance of the lens and one conjugate distance of the concave mirror Is the other conjugate point of the lens.

  Such an arrangement of Patent Document 1 (in the case of the second embodiment) has the following two drawbacks. (A) When measuring the surface shape of the measurement target with an error of 10 nanometers or less, it is necessary to set the measurement target surface with an error of 1 micron or less with respect to the front-rear direction of the measurement target surface. (B) A surface shape component that is a quadratic function in the one-dimensional scanning direction of the laser beam cannot be measured.

  In order to remove these drawbacks, the following arrangement was adopted in the examples of the present invention. The optical path S1-R-M is made equal to the radius of curvature of the concave mirror. That is, in FIG. 2, the optical path A-Q-C is equal to the radius of curvature of the concave spherical mirror.

  With such an arrangement according to the embodiment of the present invention, the propagation direction of the reflected laser beam from the measurement target surface changes due to the inclination θ of the measurement target surface, and is inclined by 2θ with respect to the optical axis of the optical system (see FIG. 3). . At this time, the position of the measurement target surface is not limited. On the other hand, in Patent Document 1, there is a limitation that the length of the optical path MQ-S2 is a conjugate distance of the concave mirror, and it is necessary to accurately set the position of the measurement target surface.

  In the embodiment of the present invention, the lens 41 is used to detect the propagation direction of the reflected laser beam (the angle 2θ tilted with respect to the optical axis of the optical system), and the light beam position detector 42 is used at the focal plane of the lens 41. Place. The position of the 2θf light beam is detected. That is, the lens 41 is not a lens for forming an image (imaging lens).

  On the other hand, in Patent Document 1, in order for the lens to detect the movement of light on the surface of the light beam turning means, an image of light on the surface of the light beam turning means is formed on the surface of the position sensor. It is arranged so that. That is, the lens here is an imaging lens.

  With the above arrangement, the above-mentioned defect (a) is eliminated, and the position setting accuracy of the measurement target surface may be about several mm. Moreover, the surface shape component which is a quadratic function can be measured by eliminating the defect (b).

  By the way, the applicant conducted a shape measurement experiment for verifying the function and effect by using the shape measuring apparatus in the present embodiment shown in FIGS.

In the shape measurement experiment, specific conditions were as follows. As the laser light source 10, a He—Ne laser light source with an output of 5 mW was used. The shape of the concave spherical mirror 22 was a rectangle of 80 mm × 15 mm, and the radius of curvature was R = 400 mm. The full width at half maximum of the beam spot on the surface of the measuring object 30 was 30 μm. The distance between the measuring object 30 and the flat mirror 21 was d = 7 mm. The focal length of the lens 41 was 200 mm. The light beam position detector 42 is a two-dimensional position detection sensor, and the position detection resolution was 1.5 μm. Therefore, the inclination angle detection resolution of the surface of the measurement object 30 was 3.5 × 10 ⁻⁶ rad. The scanner mirror 20 was attached to a servo motor capable of speed control, and the rotational angular speed of the motor was 250 rpm. Since the distance between the sample surface S and the scanner mirror was about 200 mm, the scanning speed of the beam spot on the surface of the measurement object 30 was about 5 mm / ms. The measurement object 30 was a polygon mirror, and the width of the measurement surface was 5 mm. Since the scanning time of the beam spot over 5 mm, that is, the measurement time is 1 ms, a measurement error does not occur due to mechanical vibration of 1 kHz or less which is the reciprocal of 1 ms.

  The result of measuring the surface shape of the polygon mirror is shown in FIG. Similar measurement results were obtained when the surface of the polygon mirror was moved within the range of 3 mm along the z axis. The thick line is the measurement result with this apparatus by the laser beam high-speed scanning method, and the thin line is the measurement result with the laser interferometer Wyko NT3300 (manufactured by BEIKO INSTRUMENTS). The difference between the two was 0.98 nm in terms of root mean square. In order to examine the stability of the surface shape measurement by the laser beam high-speed scanning method, repeated measurements were performed 20 times. As a result, the variation of each measurement result was 0.31 nm in terms of root mean square.

  From the result of the shape measurement experiment, a specific effect based on the configuration of the present embodiment can be concluded as follows. Since the measurement result of the surface shape does not change even when the measurement target surface is moved back and forth, the position setting accuracy of the measurement target surface may be about several millimeters. Since the scanning speed of the beam spot on the surface to be measured is as high as about 5 mm / ms, the measurement time is as short as millisecond order, and no vibration isolator is required for measurement. Since it has the above characteristics, this shape measuring apparatus exhibits its usefulness in in-process measurement in which many mechanical vibrations exist.

  As described above, in the shape measuring method and apparatus of the present embodiment, the light beam emitted from the laser light source 10 is scanned on the surface of the measurement object 30 by the scanning optical system, and the reflected light beam reflected by the measurement object 30 is propagated. A shape measurement method for obtaining the surface shape of the measuring object 30 by detecting the direction by the light propagation direction detection system and performing the calculation based on the detection result (or calculating by the personal computer 51 as the calculation device based on the detection result) Scanner mirror 20 as a light beam diverting means for changing the light beam emitted from the laser light source 10 in a desired direction. A plane mirror 21 that reflects the light beam redirected by the scanner mirror 20, and a light beam reflected by the plane mirror 21 and incident on the measurement object 30. And the optical path length AQC from the scanner mirror 20 to the concave spherical mirror 22 via the plane mirror 21 is equal to the radius of curvature of the concave spherical mirror 22. A plane mirror 21 and a concave spherical mirror 22 are arranged, and the light propagation direction detection system is configured so that a reflected light beam reflected by the measurement object 30 is incident on the lens 41 and the focal length f of the lens 41 from the lens 41. The light beam position detector 42 is arranged at a distant position.

  In this way, since the surface shape can be measured because the propagation direction of the reflected light beam from the measurement target surface varies depending on the inclination of the measurement target surface, the optical system can accurately detect angular shake. Therefore, there are no strict conditions for the position setting accuracy of the measuring object 30, and the surface shape including the surface shape component of the quadratic function can be measured accurately. Therefore, it is possible to provide a shape measuring method and apparatus capable of accurately measuring a surface shape including a surface shape component of a quadratic function without strict conditions on the position setting accuracy of the measurement object 30.

  Further, in the shape measuring method and apparatus of the present embodiment, the reflected light beam reflected by the measuring object 30 is configured to be reflected by the scanner mirror 20, and the reflected light beam reflected by the scanner mirror 20 is reflected toward the lens 41. A second plane mirror 40 is disposed.

  In this way, since the light propagation direction detection system can be arranged at a position away from the scanning optical system, it is easy to configure an apparatus (shape measuring apparatus) used for the shape measurement.

  Further, in the shape measuring method and apparatus of the present embodiment, the detection position Δ (Δ = 2θf, θ is the inclination angle of the surface of the measurement target, f is the detection result of the light beam position detector 42 as the detection result of the light propagation direction detection system. Is obtained by sequentially calculating the inclination angle θ based on the focal length), measuring the position distribution Δ (x) of the detection position Δ with respect to the scanning direction position x, and calculating the following equation:

The surface shape r (x) of the measurement object is obtained.

  In this way, the surface shape of the measuring object 30 can be easily calculated from the detection position of the light beam position detector 42.

  In addition, this invention is not limited to the said Example, It can change in the range which does not deviate from the meaning of this invention.

It is explanatory drawing which shows the measurement principle of the shape measuring method and apparatus in this invention. It is explanatory drawing which shows the propagation path of the laser beam in a shape measuring apparatus when there is no inclination of a measuring object surface same as the above. It is explanatory drawing which shows the propagation path of the laser beam in a shape measuring apparatus when there exists an inclination angle of the surface of a measurement object same as the above. It is a perspective view which shows schematic structure of a shape measuring apparatus same as the above. It is a characteristic view which shows the measurement experiment result by a shape measuring apparatus same as the above.

Explanation of symbols

10 Laser light source
20 Scanner mirror (light flux redirecting means)
21 Flat mirror
22 concave spherical mirror
30 Measurement target
40 plane mirror (second plane mirror)
41 Lens
42 Light beam position detector
51 PC (arithmetic unit)

Claims (6)

The light beam emitted from the light source by the scanning optical system is scanned on the surface of the measurement object, the propagation direction of the reflected light beam reflected by the measurement object is detected by the light propagation direction detection system, and the calculation is performed based on the detection result. A shape measuring method for obtaining a surface shape of the measurement object by performing,
The scanning optical system is configured to change a light beam emitted from the light source in a desired direction, a light beam diverting unit, a plane mirror that reflects the light beam diverted by the beam diverting unit, and the plane mirror. And a concave spherical mirror that reflects the light beam reflected by the plane mirror and makes it incident on the object to be measured, and the light beam is transmitted from the beam redirecting means via the plane mirror to the concave spherical surface. The plane mirror and the concave spherical mirror are arranged so that the optical path length to the mirror is equal to the radius of curvature of the concave spherical mirror,
The light propagation direction detection system comprises a lens on which a reflected light beam reflected by the measurement object is incident, and an optical position detector disposed at a position separated from the lens by a focal length of the lens. The shape measurement method. A reflected light beam reflected by the measurement object is reflected by the light beam diverting means, and a second plane mirror is provided for reflecting the reflected light beam reflected by the light beam diverting means toward the lens. The shape measuring method according to claim 1, wherein: The inclination angle θ is determined based on the detection position Δ of the optical position detector (Δ = 2θf, θ is the inclination angle of the surface of the measurement object, and f is the focal length), which is the detection result of the light propagation direction detection system. By sequentially calculating, the position distribution Δ (x) with respect to the scanning direction position x of the detection position Δ is measured, and by calculating the following equation:

3. The shape measuring method according to claim 1, wherein a surface shape r (x) of the measurement object is obtained. The light beam emitted from the light source by the scanning optical system is scanned on the surface of the measurement object, the propagation direction of the reflected light beam reflected by the measurement object is detected by the light propagation direction detection system, and the arithmetic unit is based on the detection result A shape measuring device for obtaining the surface shape of the measurement object by performing an operation in
The scanning optical system is configured to change a light beam emitted from the light source in a desired direction, a light beam diverting unit, a plane mirror that reflects the light beam diverted by the beam diverting unit, and the plane mirror. And a concave spherical mirror that reflects the light beam reflected by the plane mirror and makes it incident on the object to be measured, and the light beam is transmitted from the beam redirecting means via the plane mirror to the concave spherical surface. The plane mirror and the concave spherical mirror are arranged so that the optical path length to the mirror is equal to the radius of curvature of the concave spherical mirror,
The light propagation direction detection system comprises a lens on which a reflected light beam reflected by the measurement object is incident, and an optical position detector disposed at a position separated from the lens by a focal length of the lens. A shape measuring device. A reflected light beam reflected by the measurement object is reflected by the light beam diverting means, and a second plane mirror is provided for reflecting the reflected light beam reflected by the light beam diverting means toward the lens. The shape measuring apparatus according to claim 4, wherein The arithmetic unit is based on the detection position Δ of the optical position detector (Δ = 2θf, θ is the inclination angle of the surface of the measurement object, and f is the focal length) which is the detection result of the light propagation direction detection system. By sequentially calculating the tilt angle θ, the position distribution Δ (x) of the detection position Δ with respect to the scanning direction position x is measured, and the following equation is calculated:

6. The shape measuring apparatus according to claim 4, wherein the surface shape r (x) of the measurement object is obtained.

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